On 32 bit systems, the following kernel BUG is hit:
BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
caller is debug_smp_processor_id+0x18/0x24
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.19.0-rc1-00001-g6ae0aec8a366 #181
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
Backtrace:
dump_backtrace from show_stack+0x20/0x24
r7:81024ffd r6:00000000 r5:81024ffd r4:60000013
show_stack from dump_stack_lvl+0x60/0x78
dump_stack_lvl from dump_stack+0x14/0x1c
r7:81024ffd r6:80f652de r5:80bec180 r4:819a2500
dump_stack from check_preemption_disabled+0xc8/0xf0
check_preemption_disabled from debug_smp_processor_id+0x18/0x24
r8:8119b7e0 r7:81205534 r6:819f5c00 r5:819f4c00 r4:c083d724
debug_smp_processor_id from __spi_sync+0x78/0x220
__spi_sync from spi_sync+0x34/0x4c
r10:bb7bf4e0 r9:c083d724 r8:00000007 r7:81a068c0 r6:822a83c0 r5:c083d724
r4:819f4c00
spi_sync from spi_mem_exec_op+0x338/0x370
r5:000000b4 r4:c083d910
spi_mem_exec_op from spi_nor_read_id+0x98/0xdc
r10:bb7bf4e0 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:82358040
r4:819f7c40
spi_nor_read_id from spi_nor_detect+0x38/0x114
r7:82358040 r6:00000000 r5:819f7c40 r4:819f7c40
spi_nor_detect from spi_nor_scan+0x11c/0xbec
r10:bb7bf4e0 r9:00000000 r8:00000000 r7:c083da4c r6:00000000 r5:00010101
r4:819f7c40
spi_nor_scan from spi_nor_probe+0x10c/0x2d0
r10:bb7bf4e0 r9:bb7bf4d0 r8:00000000 r7:819f4c00 r6:00000000 r5:00000000
r4:819f7c40
per-cpu access needs to be guarded against preemption.
Fixes: 6598b91b5ac3 ("spi: spi.c: Convert statistics to per-cpu u64_stats_t")
Reported-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: David Jander <david@xxxxxxxxxxx>
---
drivers/spi/spi.c | 5 ++++-
include/linux/spi/spi.h | 10 ++++++++--
2 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index d94822bf3cec..ac61824b87b5 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -314,11 +314,13 @@ static void spi_statistics_add_transfer_stats(struct spi_statistics *pcpu_stats,
struct spi_controller *ctlr)
{
int l2len = min(fls(xfer->len), SPI_STATISTICS_HISTO_SIZE) - 1;
- struct spi_statistics *stats = this_cpu_ptr(pcpu_stats);
+ struct spi_statistics *stats;
if (l2len < 0)
l2len = 0;
+ get_cpu();
+ stats = this_cpu_ptr(pcpu_stats);
u64_stats_update_begin(&stats->syncp);
u64_stats_inc(&stats->transfers);
@@ -333,6 +335,7 @@ static void spi_statistics_add_transfer_stats(struct spi_statistics *pcpu_stats,
u64_stats_add(&stats->bytes_rx, xfer->len);
u64_stats_update_end(&stats->syncp);
+ put_cpu();
}
/*
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 2e63b4935deb..c96f526d9a20 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -84,18 +84,24 @@ struct spi_statistics {
#define SPI_STATISTICS_ADD_TO_FIELD(pcpu_stats, field, count) \
do { \
- struct spi_statistics *__lstats = this_cpu_ptr(pcpu_stats); \
+ struct spi_statistics *__lstats; \
+ get_cpu(); \
+ __lstats = this_cpu_ptr(pcpu_stats); \
u64_stats_update_begin(&__lstats->syncp); \
u64_stats_add(&__lstats->field, count); \
u64_stats_update_end(&__lstats->syncp); \
+ put_cpu(); \
} while (0)
#define SPI_STATISTICS_INCREMENT_FIELD(pcpu_stats, field) \
do { \
- struct spi_statistics *__lstats = this_cpu_ptr(pcpu_stats); \
+ struct spi_statistics *__lstats; \
+ get_cpu(); \
+ __lstats = this_cpu_ptr(pcpu_stats); \
u64_stats_update_begin(&__lstats->syncp); \
u64_stats_inc(&__lstats->field); \
u64_stats_update_end(&__lstats->syncp); \
+ put_cpu(); \
} while (0)
/**
--
2.32.0
